Device for projecting an image

ABSTRACT

According to the present invention there is provided a projection device, which is configured to project an image which is co-operable with images projected by one or more other projection devices, wherein the projection device comprises a detector operable to detect characteristics of images projected on a display surface by the projection device and one or more other projection devices, and a controller operable to adjust the projection device and/or to adjust one or more of the other projection devices, based on the characteristics of the images detected by the detector, such that the images projected by each projection device co-operate on the display surfaces.

RELATED APPLICATION

This application is a Continuation of PCT/EP2011/065184, filed Sep. 2,2011, which claims priority from PCT/EP2010/063327, filed Sep. 10, 2010,the subject matter of which are incorporated herein by reference intheir entirety.

FIELD OF THE INVENTION

The present invention relates to a device for projecting an image, inparticular, but not exclusively, to a device for projecting an image ofincreased brightness and/or of increased size, wherein the image can beprojected as a 2-D image or a 3-D image.

BACKGROUND TO THE INVENTION

A MEMS micro-mirror device is a device that contains aMicro-Electrical-Mechanical-System with a reflective surface. Theoptical MEMS may comprise a cylindrical, elliptical, rectangular orsquare micro-mirror that is adapted to move and to deflect light overtime. The micro-mirror is connected by suspended arms to a fixed partand can tilt and oscillate along one or two axis. For example it canoscillate vertically and horizontally. Different actuation principlescan be used, including electrostatic, thermal, electro-magnetic orpiezoelectric. MEMS devices are known in which the area of thesemicro-mirrors are around a few mm2. In this case, the dimensions of theMEMS device, comprising the packaging, is around ten mm2. This device isusually made of silicon, and can be encapsulated in a package that caninclude the driving actuation electronics. Various optical components,such as for example lenses, beam combiner, quarter-wave plates, beamsplitter and laser chips, are assembled with the packaged MEMS to builda complete device.

A typical application of the MEMS micro-mirror devices is for projectiondevices. In a projection device, a 2-D image or a video can be displayedon any type of surface. In a color device, each pixel is generated bycombining modulated red, green and blue laser light sources, by meansof, for example, a beam combiner. A MEMS micro-mirror device directs thelight of the laser light source to a projection surface and reproducesthe image, or the video, pixel-by-pixel. By means of its oscillations,the micro-mirror within the device will continuously scan from left toright and from top to bottom, or according to a different trajectoryincluding e.g., Lissajou trajectories, so that each pixel of the 2-Dimage is displayed on the screen.

Typically, the micro-mirror of a MEMS micro-mirror device is able tooscillate along one axis. Therefore, in order to display a 2-D image ona screen a projection device will require two MEMS micro-mirror devices;a first MEMS micro-mirror device is required to deflect light along thehorizontal image axis and a second MEMS micro-mirror device is requiredto deflect light along the vertical image axis. During operation, themicro-mirror of the first MEMS micro-mirror device receives light fromthe beam combiner and deflects the light to the micro-mirror of thesecond MEMS micro-mirror device. The micro-mirror of the second MEMSmicro-mirror device will in turn deflect the light to the displaysurface where it will appear as a pixel. The micro-mirror of the firstMEMS micro-mirror device will oscillate to scan the light along thehorizontal image axis thereby displaying the first row of pixels on thedisplay surface. The micro-mirror of the second MEMS micro-mirror devicewill oscillate about its oscillatory axis so that light received fromthe micro-mirror of the first MEMS micro-mirror device is scanned alongthe vertical image axis. The combined effect of the oscillatingmicro-mirrors is that the light from the beam combiner is scanned in azig-zag or raster pattern along the display surface. The process iscontinuous so that a complete image is visible to the viewer on thedisplay surface. The first and the second MEMS micro-mirror devices areprecisely positioned such that the oscillatory axes of the respectivemicro-mirrors are orthogonal; this ensure that all the light received bythe micro-mirror of the first MEMS micro-mirror device will be deflectedto the micro-mirror of the second MEMS micro-mirror device as the micromirrors oscillate.

Other MEMS micro-mirror devices comprise a micro-mirror which canoscillate along two orthogonal axes. Such a micro-mirror can scan thelight beam in two dimensions. Therefore, to display a 2-D image on adisplay surface a single mirror will oscillate about two axes to scanthe light in a zig-zag, Lissajou or raster pattern over the displaysurface. Various methods of oscillating the micro-mirrors are employed.For example, an electrostatic means; thermal means; electro-magneticmeans, or piezoelectric means.

Projection devices in general are used to project images or videos ontoa display surface. The quality of the image projected by a projectiondevice is dependent on the brightness of the image; in contrast to abright image, the detail of a dull image will not be visible whenprojected on the display surface. Accordingly it is advantageous todisplay a bright image on the display surface so that the detail of theimage will be visible. However, in projection devices the brightness ofthe image projected on the display surface is limited by the brightnessof the light which can be provided by the light source of the projectiondevice. The brightness of the light which can be provided by a lightsource is limited by the electrical capabilities of the light source(e.g., the wattage of a light-bulb, LED or laser diode in the lightsource). Consequently, there exists a maximum brightness at which aprojection device can display an image. There is a need in the art for ameans and method which will enable increasing the brightness of an imagewhich does not require modification of the projection device.

The dimensions of an image projected by a projection device onto adisplay surface are also limited. To increase the size of the imageprojected onto a display surface requires adjustment of a focus lens ofthe projection device such the light corresponding to each pixels isspread over a larger area of the display surface. Increasing the size ofthe image will compromise the quality of the image as the sharpness, thepixel density and the brightness of the image will decrease. There is aneed in the art for a means and method for enabling enlargement of aprojected image without compromising the quality of the image.

Additionally, there is a need in the art for a simplified means whichwill enable increasing the brightness of an image and/or enablingenlargement of a projected image.

US20090257031 discloses the use of a microprocessor to physically movetwo projectors so that their projected images are aligned on the displayscreen. Precise positioning of the projectors relative to one another isdifficult to achieve. Furthermore, the device of US20090257031 requiresthat the projectors are connected by means of a linkage so as to allowthe microprocessor to position the projectors relative to one another toachieve the desired alignment of images. Thus, the device disclosed inUS20090257031 does not permit the projectors to be independent from oneanother.

It is an aim of the present invention to obviate or mitigate one or moreof the aforementioned disadvantages.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided amethod for projecting an image onto a display surface, comprising thesteps of:

a. providing two or more projection devices;

b. arranging the two or more projection devices such that they eachproject an image on a display surface;

c. off-setting an oscillating reflective surface within at least one ofthe two or more projection devices such that the image projected by eachof the two or more projection devices are in co-operation on the displaysurface.

The two or more projection devices may be independent of one another.

Each projection device is configured to project the same image content.Each projection device is configured to project the same image.

Each projection device is configured to project part of a completeimage.

When each projection device is configured to project the same image, thetwo or more projection devices are each configured such that the imageprojected by each of the two or more projection devices co-operate byoverlapping. When the images projected by each of the projection deviceoverlap, the overall brightness of the image visible on the displaysurface is increased. The overlapping of the images on the displaysurface allows the light projected by each projection device to becombined on the display surface, thereby providing a brighter image. Forexample, a first projection device may be configured to project an imageonto a display surface; a second projection device may be configured toproject the same image onto the same position on the display surface.The light projected by the second projection device is superposed on theimage projected by the first projection device so that a brighter imageis visible on the display surface.

When each projection device is configured to project part of a completeimage, the two or more projection devices are each configured such thatthe image projected by each of the two or more projection devicesco-operate by aligning. Aligning the images enables the image projectedby the two or more plurality of projection devices to be combined toform a single larger image on the display surface. For example, a firstprojection device may project an image which forms a first half of acomplete image and a second projection device may project an image whichform a second half of a complete image, the first and second projectiondevices may each be configured such that the images they projectco-operate by aligning on the display surface. When the first half ofthe complete image and the second half of the complete image are inalignment, a complete image will be visible on the display surface. Thecomplete image will be larger than an image of the same quality whichcould be projected by any one of the projections devices alone.Advantageously, unlike ‘video-walls’ there is no border between theimages projected by each projection device, so a complete image which iswithout gaps, borders or spaces, will be visible on the display surface.

According to a variant of the present invention the two or moreprojection devices may each project an image, wherein the imageprojected by each projection device comprises a portion of theresolution of a complete image to be displayed on the display surface.The two or more projection devices may be configured such that the imageprojected by each of the projection device co-operate by meshing. Forexample, each of the projection devices may project an image, whereinthe image projected by each projection device comprises a portion of thepixels required to display a complete image, to be displayed on thedisplay surface. The images projected by each of the projection devicesco-operate on the display screen to display an image of improvedresolution. Advantageously, with ‘N’ projectors with a definedresolution, an image of ‘N’ times higher resolution can be displayed onthe display surface. For example, a first projection device may projecta first image on the display surface, the first image comprising half ofthe pixels of the complete image to be displayed on the display screen.A second projection device may project a second image on the displaysurface, the second image comprising the other half of the pixels of thecomplete image to be displayed on the display surface. Both projectiondevices are configured such that the image projected by each projectiondevice co-operate by meshing on the display surface, to display acomplete image on the display surface. The meshing of the first andsecond images ensures that successive pixels of the complete image areprojected by the first and second projection devices alternately. Itwill be understood that the successive pixels of the complete image areprojected by the first and second projection devices either,alternately, consecutively or progressively. The successive pixels ofthe complete image may be projected by the first and second projectiondevices such the pixels projected by each of the first and secondprojection devices are interlaced. The complete image therefore hastwice the resolution of an image which could be projected by either oneof the first or second projection devices alone. The complete imagetherefore has twice the resolution of an image which could be projectedby either one of the first or second projection devices alone.

The method may further comprise detecting characteristics of the imagesprojected by some or all of the two or more projection devices.

The method may further comprise the step of detecting the position onthe display surface of the image projected by a projection device.Preferably, the method further comprises the step of detecting theposition on the display surface of the image projected by each of thetwo or more projection devices. The two or more projection devices maybe configured such that the image projected by each of the projectiondevice are in co-operation on the display surface, based on the detectedposition of the images projected.

The method may further comprise detecting the size of the imagesprojected by some or all of the two or more projection devices.

The method may further comprise detecting the shape of the imageprojected by some or all of the two or more projection devices.

The method may further comprise detecting the brightness of the imagesprojected by some or all of the two or more projection devices.

The method may further comprise the step of off-setting a reflectivesurface of a projection device. The method may further comprise the stepof off-setting one or more reflective surfaces of the two or moreprojection devices. Preferably, the method comprises the step of,applying a DC off-set to a reflective surface to off-set the reflectivesurface. Off-setting the reflective surface will adjust direction inwhich the projection device projects, accordingly off-setting thereflective surface can be used to move the position of the projectedimage such that the projected image co-operates with an image projectedby one or more other projection devices.

The method may further comprise the step of modifying the speed at whicha reflective surface of a projection device oscillates. The method mayfurther comprise the step of modifying the speed at which one or morereflective surfaces of the two or more projection devices oscillate. Themethod may comprise modifying an actuation signal which is used tooscillate a reflective surface in a projection device. For example, theamplitude of actuation signals used to oscillate reflective surfaces ineach of the two or more projection devices may be increased ordecreased. Increasing the amplitude of the actuation signal willincrease the amplitude of oscillation of the reflective surface;accordingly the light projected from the projection devices will beprojected over a wider span of the display surface, thereby increasingthe size of the images projected by the projection device. Optionally,the modulation of the laser source may also be modified to decrease thespeed at which the light pulses are generated by the laser source whenthe amplitude of oscillation of the reflective surface is increased;this will ensure that gaps to not appear between successive pixels onthe display surface. Decreasing the amplitude of the actuation signalmay decrease the amplitude of oscillations of the reflective surface;accordingly the light projected from the projection device will beprojected over a shorter span of the display surface, thereby decreasingthe size of the image projected. Optionally, the modulation of the lasersource may also be modified to increase the speed at which the lightpulses are generated by the laser source when the amplitude ofoscillation of the reflective surface is decreased; this will ensurethat the pixels belonging to a particular row do not appear on anotherrow, thereby not distorting the image.

The method may further comprise the step of, modifying the modulation ofa light source in a projection device. Modifying the modulation of alight source in a projection device can alter the size of the imageprojected on the display surface. For example, modifying the modulationof a light source in a projection device can crop the image projected onthe display surface, thereby decreasing the size of the image visible onthe display surface. For example, the light source in a projectiondevice may be a laser source; light pulses may be generated by the lasersource, each light pulse corresponding to a pixel of the image to beprojected onto a display surface. The light from the laser source may bescanned across the display surface by a micro-mirror within theprojection device. For example, the micro-mirror may oscillate about atwo orthogonal oscillation axes to scan the laser light in a zig-zag,lissajou, or raster pattern along the display surface, so that the imageis projected, pixel-by-pixel, onto the display surface. If themodulation of the laser source is now modified to increase the speed atwhich the light pulses are generated then, assuming the speed ofoscillation of the micro-mirror remains the same, the space betweenconsecutive pixels on the display surface will be reduced. Accordingly,a smaller image will be visible on the display surface. Furthermore,increasing the speed of the light pulses generated by the laser sourcewill ensure that each row of pixels of the image will be projected priorto the micro-mirror completing full oscillations. Accordingly, the imageis cropped or shrinked and a smaller image will be visible on thedisplay surface.

The reflective surface may be a mirror. For example, the reflectivesurface may be a MEMS micro mirror. The reflective surface may be a DLP,LCOS, LCD, TFT and or OLED.

The method may further comprise the step of adjusting the brightness ofthe light projected by one or more of the projection devices.Preferably, the brightness of the light projected by one or more of theprojection devices is adjusted so that the brightness of the lightprojected by each projection device is uniform. The brightness of thelight projected by one or more of the projection devices may be adjustedso that the brightness of the light projected by each projection deviceis non uniform

The image projected by each of the projection devices may be a testimage which is used to determine how the two or more projection devicesshould be configured such that the image projected by each of theprojection device are in co-operation on the display surface.

According to a further aspect of the present invention there is provideda method of projecting a 3-D image comprising the steps of:

d. Providing two or more projection devices;

e. arranging the two or more projection devices into a first group andsecond group, wherein the first group and second group each comprise oneor more projection devices;

f. arranging the first and second group of projection devices such thateach group of projection devices can project an image on a displaysurface, wherein the first group of projection devices is arranged suchthat the first group of projection devices can project an image to afirst position on the display surface and the second group of projectiondevices is arranged such that the second group of projection devices canproject an image to a second position on the display surface, whereinthe first and second positions off-set from one another;

g. configuring the first and second group of projection devices suchthat the first and second group of projection devices alternatelyproject onto the display surface.

Preferably, the first and second positions are off-set from one anotherby an amount required to form 3-D image on the display surface.Preferably, the off-set is substantially equal to the average distancebetween a human's left eye and a humans right eye. Preferably, theoff-set is between 0 cm-11 cm. More preferably, the off-set is between0.1 cm-3 cm.

According to a further aspect of the present invention there is provideda projection device, which is configured to project an image which isco-operable with images projected by one or more other projectiondevices, wherein the projection device comprises,

h. a detector operable to detect characteristics of images projected bythe projection device and the one or more other projection devices and

i. a controller operable to adjust the projection device and/or the oneor more other projection devices, based on the characteristics of theimages detected by the detector, such that the images projected by eachprojection device co-operate on a display surface.

The controller may be operable to adjust a reflective surface withinprojection device and/or to adjust a reflective surfaces within the oneor more other projection devices, based on the characteristics of theimages detected by the detector, such that the images projected by eachprojection device co-operate on the display surface.

According to a further aspect of the present invention there is provideda projector arrangement comprising a plurality of projection devicesaccording to the previous paragraph.

The detector may be configured to detect at least one of thecharacteristics of the images selected from the group of comprising; theposition of the image on the display surface; the size of the image onthe display surface; the shape of the image on the display surface thebrightness of the image.

The detector may comprise one or more CCD camera or/and one or more CMOScamera or/and one or more photodiodes.

The detector may comprise a means for one or more of the following: selfmixing; image projection analysis using a camera to analyze an image;time of flight measurement by measuring the time of flight of a signalwhich defines a pixel, or signals which define a group of pixels, in aprojected image (the time of flight of the signals can be measuredsimultaneously with the projected pixel or successively); measuring timeof flight of a signal which defines a pixel, or signals which define agroup of pixels, in a projected image, using a single photodiode;carrying out triangulation using two or more cameras; projecting apatterned test image and measuring deformation of the patterned image;carrying out acoustic analysis using an acoustic sensor.

The controller may be operable to adjust a projection device, based onthe characteristics of the images detected by the detector, to changethe size, shape, position, and/or brightness of the image projected bythe projection device. The controller may be operable to adjust anotherprojection device, based on the characteristics of the images detectedby the detector, to change the size, position, shape and/or brightnessof the image projected by the projection device.

The controller may be configured to change the image projected by theprojection device. The controller may be configured to change the imageprojected by another projection device. For example, the controller maychange the colour of an image so as to compensate for the colour of thedisplay surface.

The controller may operate automatically without requiring user input toadjust the projection device.

The controller may be operable to adjust the projection devices suchthat the images projected by the projection devices co-operate byoverlapping. The controller may be operable to adjust the projectiondevices such that the images projected by each projection devicesco-operate by aligning. The controller may be operable to adjust theprojection devices such that the images projected by each projectiondevices co-operate by overlapping and aligning. For example; if the userdesires a specific image size or image resolution that cannot beachieved by means of overlapping or aligning only, in this case thecontroller may adjust the projection device and the one or more otherprojection devices, to achieve the desired image size or resolution, byoverlapping and aligning the projected images.

Preferably, the controller is operable to off-set a reflective surfaceof a projection device. For example, a first projection device mayproject a first image onto a display surface and second projectiondevice may project the same image onto a different position on displaysurface. Each of the first and second projection devices project imagesin the same manner: light pulses corresponding to an image pixel, aregenerated in a light source of the each projection device; a reflectivesurface in each projection device, in the form of a MEMS micro mirror,is oscillated about two orthogonal oscillation axis by means of analternative (AC) actuation signal (e.g., an AC voltage) which is appliedto the actuator(s) (e.g., piezoelectric, electrostatic, thermal and/ormagnetic actuators) which co-operate with the MEMS micro mirrors, toscan the light pulses in a zig-zag, lissajou or raster pattern acrossthe display surface to display the image on the display surfacepixel-by-pixel. The first projection device is a projection deviceaccording to the present invention. The detector of the first projectiondevice detects the position on the display surface of the imagesprojected by the first and second projection devices. Subsequently, thecontroller adjusts the AC actuation signals which are applied to theactuators in the first projection device, by applying a DC off-set tothe AC actuation signal, thereby causing the first projection device toproject its image to a defined location on the display surface. Thecontroller of the first projection device communicates wirelessly (orwith wire) with the second projection device and sends a command to thesecond projection device to apply a DC off-set to its actuation signal,causing the second projection device to also project its image to thedefined location on the display surface. Accordingly, the imageprojected by the first projection device and the image projected by thesecond projection device overlap on the display surface. Overlapping theimages projected by the projections devices will provide for theprojected image, visible on the display screen, with increasedbrightness. Alternatively, the controller can adjust each projectiondevice such that the images projected by each projection device are inalignment on the display surface. Alternatively, it is also possible foreach of the projections devices to comprise its own detector and acontroller. The detector and controller of each projections device canco-operate with the detectors and controllers of the other mobile phonesto achieve the desired co-operation of the images on the displaysurface. Alternatively, if each of the projections devices comprises adetector and controller, then the detector and controller of one of theprojections devices may be designated as the “master” and the detectorsand controllers of the other mobile phone designated as the “slaves”.The master detector and controller may effect adjustment of theprojection devices in the other mobile phones.

It will be understood that the light could be scanned by the MEMS micromirrors reflective surface, in a bidirectionally, unidirectionally orprogressively manner, or such that lines are interlaced.

The controller may be operable to adjust one or more projection devicessuch that the size or shape of the image projected by each projectiondevice is altered. Preferably, the controller is operable to modifyingthe amplitude at which a reflective surface in each of the one or moreprojection devices, oscillate. For example, the detector can detect thesize of the image projected by the two projection devices andsubsequently the controller can adjust each projection device such thatthey each project the same size and shape of image, by for example,modifying the amplitude at which a reflective surface in each of the twoprojection devices, oscillate.

The controller may be operable to modifying the modulation of a lightsource in one or more projection devices.

The controller may be operable to adjust the brightness of the lightprojected by a projection device. The controller may be operable toadjust the brightness of the light projected by each of the projectiondevices. Preferably, the controller is operable to adjust the brightnessof the light projected by the projection device and the one or moreprojection devices such that brightness of a complete image which isdefined by image portions projected by the projection device and the oneor more other projection device, is uniform.

The controller may be operable to calculate an optimum position on thedisplay surface for projection of the image. Projecting the image at theoptimum position will minimise the required overall adjustment of theprojection devices in order to achieve the desired co-operation of theimages on the display surface.

The projection device may comprise a means for detecting gestures madeby a user. The projection device may comprise a means for detecting anobject; for example the device may comprise a means for detecting apointer which is positioned on an image. The projection device maycomprise a means for providing the projected images with tactilefunctionality. The projection device may further comprise a means fordetecting an interaction of a user with a projected image. For examplethe projection device may comprise a means for detecting touching of aprojected image by a user.

The projection device may further comprise a means to detectcharacteristics of a display surface. The projection device may furthercomprise a means to adjust the projection device to compensate forirregularities detected on the display surface. For example, the displaysurface may be uneven, and the projection device may be adjusted toaccount for the uneven surface so that an undistorted image is visibleto a viewer; or the display surface may not comprise a uniform colour,and the projection device may be adjusted to compensate for the colourdifference across the display surface; thus ensuring that the colours ofthe projected image are not distorted by the colours of the displaysurface.

The projection device may further comprise a means for off-setting areflective surface of a projection device. The projection device mayfurther comprise a means for off-setting a reflective surface of two ormore projection devices. The means for off-setting a reflective surfacemay comprise a means for applying a DC off-set to a reflective surfaceto off-set the reflective surface. Off-setting the reflective surfacewill adjust direction in which the projection device projects,accordingly off-setting the reflective surface can be used to move theposition of the projected image such that the projected imageco-operates with an image projected by one or more other projectiondevices.

The projection device may further comprise a means for off-setting areflective surface of a projection device to avoid an obstaclepositioned in a projection path of the projection device. The projectiondevice may further comprise a means for off-setting a reflective surfaceof a projection device to avoid an area of the display surface which isnot suitable for displaying a projected image. The projection device mayfurther comprise a means for off-setting a reflective surface of aprojection device to avoid an obstacle obstructing a display surface.

A reflective surface may be off-set using at least one of; applying a DCoff-set signal to an actuation signal which actuates the oscillation ofthe reflective surface in a projection device; off-setting the positionof a holder which holds a reflective surface in the projection device;off-setting a second reflective surface which cooperates with areflective surface in a projection device.

The projection device may comprise a means for proposing to a userdifferent positions on the display surface onto which to project. Forexample a projection system may project randomly to a plurality ofdifferent positions. The projection system may request the user tochoose one of the plurality of positions onto which to project.

The projection device may be configured to project a test image which isused to determine how the two or more projection devices should beconfigured such that the image projected by each of the projectiondevice are in co-operation on the display surface. The projection devicemay be configured to project a test image which is used to determine oneor more characteristics of a display surface.

The projection device may comprise a means for selectively configuringprojection device to project underexposed, overexposed, or correctlyexposed image. The projection device may comprise a means forselectively configuring another projection device to projectunderexposed, overexposed, or correctly exposed image. The projectiondevice may comprise a means to adjust the projection device such that aprojection device projects one of either an overexposed image,underexposed image or correctly exposed image, and wherein the device isoperable to adjust at least one other projection device such that the atleast one other projection device projects one of an overexposed image,underexposed image or correctly exposed image, wherein the exposure ofthe image projected by the projection device is different to theexposure of the image projected by the at least one other projectiondevice, wherein the projected images cooperate on the display surface todefine a single image which has improved brightness and clarity. Theprojection device may comprise a means for configuring a firstprojection device to project an underexposed image, configuring a secondprojection device to projection an overexposed image, and a thirdprojection device to project a correctly exposed image. The projectiondevice may comprise a means for ensuring that each of the underexposedimage, overexposed image, correctly exposed image, are projected to thesame position on a display surface, where the images can cooperate. Theimages may cooperate to provide a high dynamic range image. It will beunderstood that the images may be frames of a video. The controller maybe configured to adjust the projection device and other projectionsdevices.

The projection device may comprise a means for dimming the brightness ofan image projected by the projection device. The projection device maycomprise a means for dimming the brightness of an image projected by oneor more another projection device. The projection device may comprise ameans for adjusting at least one of the following parameters of an imageprojected by the projection device; contrast, tone, colour gamut,saturation, colour balance, brightness, adaptive image ISO. Theprojection device may comprise a means for adjusting at least one of thefollowing parameters of an image projected by one or more projectiondevice; contrast, tone, colour gamut, colour balance, brightness,adaptive image ISO. This may enable the projected image to be providedwith increased perceived brightness and/or readability.

The projection device may comprise a filter for filtering a projectedimage. The projection device may comprise a means for filtering at animage projected by the projection device. The projection device maycomprise a means for filtering at an image projected by anotherprojection device. The filter or means for filtering may be configuredto filter colour, attenuation, blur, sharpener, artistic, brush strokes,sketch, stretch, render, stylize, distortion, pixelization, shadow,digitization, edge sharpen, equalizer, night vision, panorama, red eyeeraser, texture, noise in a projected image. These parameters can beapplied either in fixed range or in dynamic range.

The projection device may comprise a first mirror which is configuredsuch that it can oscillate along an oscillation axis to scan light onthe display surface; and a second mirror which is configured such thatit can oscillate along an oscillation axis to scan light on the displaysurface, wherein the first and second mirrors are in opticalcommunication; wherein the first mirror is configured to oscillatefaster than the second mirror; and wherein the device further comprisesa means to adjust the projection device such that the second mirror canscan light in the horizontal direction and the first mirror can scanlight in the vertical direction.

The projection device may further comprise a means to adjust theprojection device and one or more of the other projection devices suchthat the images projected by the projection device and the one or moreother projection devices overlap on the display screen. Preferably theimages will directly overlap one another; i.e., will have the same sizeand be projected to the same position on the display screen.

Preferably, the first mirror which is configured such that it canoscillate along an oscillation axis to scan light in a horizontaldirection and a second mirror which is configured such that it canoscillate along an second oscillation axis to scan light in a verticaldirection, before the projection device is adjusted. The first andsecond oscillation axis may be orthogonal.

Adjusting the projection device such that the scanning of the first andsecond mirrors is inverted so that the fast oscillating mirror scanslight vertically and the slow oscillating mirror scans lighthorizontally, and overlapping the projected image with images (whichhave the same image content) projected by one or more other projectionsystems which have a typical fast oscillating mirror which scans lighthorizontally and a slow oscillating mirror which scan light vertically,will result in a projected image which has increased pixel density andprovide for a more readable projected image.

The means to adjust the projection device may comprise a means to invertthe oscillation axis of the first and second mirrors.

The means to adjust the projection device may comprise a means to tiltthe projection device. Preferably, the means to tilt the projectiondevice will be operable to tilt the projection device by at least 90°.

According to a further aspect of the present invention there is provideda projection device, which is configured to project an image which isco-operable with images projected by one or more other projectiondevices, wherein the projection device comprises

j. a receiver, configured to receive commands from a controller ofanother projection device.

Preferably, the receiver is configured to receive commands from acontroller of a projection device according to any of theabove-mentioned projection devices.

The projection device may comprise a controller configured to executethe commands received.

According to a further aspect of the present invention there is provideda mobile device comprising any of the above-mentioned projectiondevices.

The mobile device may be at least one selected from the groupcomprising, a mobile phone, digital camera, laptop computer, tablet,smart-phone, or any other consumer mobile device.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described by way of exampleonly, with reference to the accompanying drawings in which,

FIG. 1 provides a perspective view of four mobile phones, each of whichcomprises a projection device according to the present invention,wherein the projection device of each mobile phone is arranged toproject an image onto a display surface;

FIG. 1 a provides a perspective view of a projection device which eachof the mobile phones shown in FIG. 1 comprise;

FIG. 2 illustrates the features which are common to the projectiondevices of each of the mobile phones shown in FIG. 1;

FIG. 3 illustrates a alternative configuration for the projectiondevices of the mobile phones shown in FIG. 1;

FIG. 4 provides a perspective view of the four mobile phones shown inFIG. 1 after a method according to one embodiment of the presentinvention has been implemented;

FIG. 5 provides a perspective view of the four mobile phones shown inFIG. 1 after a method according to further embodiment of the presentinvention has been implemented.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a perspective view of four mobile phones 2,4,6,8. Eachof the mobile phones 2,4,6,8 comprises a projection device 102,104,106,108 which projects an image 12,14,16,18 onto a display surface 10. Thefour mobile phones 2,4,6,8 each have a different orientation,accordingly, the positions of their respective projected images12,14,16,18 on the display surface 10 is different.

FIG. 1 a provides a perspective view of the projection device102,104,106, 108 which each mobile phone 2,4,6,8 comprises. As shown inthe figure the projection device 102,104,106, 108 comprises a beamcombiner 800, a beam splitter 403 and two packages 405,407 each of whichhouses a micro mirror (not shown) which can deflect light from the beamsplitter to the display screen (not shown).

FIG. 2 illustrates one possible configuration for the features which arecommon to each projection device 102,104,106, 108 of each mobile phone2,4,6,8. Each projection device comprises alight source 120 whichcomprises a red 122, green 124 and blue 126 lasers, each of whichprovides light which is combined in a beam combiner 128 to generatelight pulses 4. Each light pulse 4 corresponds to a pixel of an image130 (or video) to be projected onto the display surface 10. Eachprojection device 102,104,106, 108 comprises a housing 70 whichcomprises a fixed reflective element 121 and a MEMS micro mirror 132supported therein. The MEMS micro mirror 132 is configured to oscillateabout two orthogonal oscillation axes 134,136.

During operation light pulses 4 passes from the beam combiner 128 to thefixed reflective element 121 via a transparent window in the housing 70.The light pulses 4 are deflected by the fixed reflective element 121 tothe MEMS micro-mirror 132. The MEMS micro-mirror 132 deflects the lightpulses 4 to the display surface 10, via a second transparent window 107in the housing 70, allowing the reproduction of the image 130 (or video)on the display surface 10. As the MEMS micro-mirror 132 deflects thelight pulses 4 to the display surface 10 it oscillates to about its twoorthogonal oscillation axes 134,136. By oscillating, the micro-mirror132 within the projection devices 102,104,106,108 will continuously scanthe light pulses in a zig-zag pattern over the display surface 10 sothat the 2-D image is displayed on the display surface 10,pixel-by-pixel.

The MEMS micro-mirror 132 is actuated to oscillate about its twoorthogonal oscillation axes 134,136 by an AC voltage actuation signalwhich is applied to piezoelectric actuators (not shown) which co-operatewith the MEMS micro mirror 132 to oscillate it about its two orthogonaloscillation axes 134,136.

An alternative to the configuration illustrated in FIG. 2, eachprojection device 102,104,106,108 may be configured as illustrated inFIG. 3. In the configuration shown in FIG. 3, instead of having onemicro-mirror which oscillates about two orthogonal axis, two MEMS micromirrors 103,105 are provided, each MEMS micro mirror 103,105 is arrangedto oscillate about a single oscillation axis 9,11 and wherein the axesof oscillation 9,11 of the MEMS micro mirrors 103,105 are perpendicular.The projection device 102,104,106,108 operates in a similar fashion tothe projection device illustrated in FIG. 2, except that the first MEMSmicro-mirror 103 oscillates about oscillation axis 9 to cause the lightpulses 4 to be deflected along the horizontal and a second MEMSmicro-mirror 105 oscillates about oscillation axis 11 to cause the lightpulses 4 to be deflected along the vertical. The combined effect of thetwo oscillating MEMS micro-mirrors 103,105 is to scan the light pulses 4in a zig-zag pattern over the display surface 10 so that the 2-D image130 is displayed on the display surface 10, pixel-by-pixel. As was thecase for the configuration shown in FIG. 2, each MEMS micro-mirror103,105 is actuated by an AC voltage actuation signal which is appliedto piezoelectric actuators (not shown) which co-operate with each of theMEMS micro mirrors 103,105 to oscillate them about their respectiveoscillation axis 9,11.

In the present example, the projection devices 102,104,106, 108 of eachof the mobile phones 2,4,6,8, shown in FIG. 1 each comprise a MEMSmicro-mirror which is configured to oscillate about two orthogonaloscillation axes (i.e., each projection device has the configurationshown in FIG. 2). Accordingly, each of the projection devices102,104,106,108 project their images 12,14,16,18 in the same manner:light pulses 4 corresponding to image pixels, are generated in a lightsource 120 of the projection device; a MEMS micro mirror 132, in eachprojection device 102,104,106,108, is oscillated about its twoorthogonal oscillation axes 134,136 by means of an actuation signal(usually an AC voltage or an AC current) applied to piezoelectricactuators (not shown) which co-operate with the MEMS micro mirror 132,to scan the light pulses 4 in a zig-zag, lissajou or raster patternacross the display surface 10 to display the image 130 on the displaysurface.

Referring once again to FIG. 1; the projection device 102, contained inmobile phone 2, further comprises a detector 22 and a controller 24. Thedetector 22 is operable to detect characteristics of the images12,14,16,18 projected by the projection devices 102,104,106,108 of eachmobile phone 2, 4,6, 8. In the present embodiment the detector 22 isoperable to detect, the position of each image 12,14,16,18 on thedisplay surface 10, the brightness of each image 12,14,16,18, the shapeof each image 12, 14, 16, 18 and the dimensions of each image12,14,16,18. It will be understood that the detector 22 could beconfigured to detect other characteristics of each image 12, 14, 16, 18in addition to image's position, brightness, shape and dimensions. Inthe present embodiment the detector 22 is a CCD or CMOS camera or aphotodiode, however it will be understood that the detector 22 may takeany other suitable form.

The controller 24 is operable to adjust the projection device 102, andthe projection devices 104,106,108 in the other mobile phones 4,6,8,based on the characteristics of the images 12,14,16,18 detected by thedetector 22. The controller 24 is in wireless communication (asillustrated by zig-zag arrows) with the projections devices 104,106,108of the other mobile phones 4,6,8, via a wireless communication means(not shown). In order to adjust the projection devices 104,106,108 ofthe other mobile phones 4,6,8, the controller 24 sends adjustmentcommands to the projection devices 104,106,108 of the other mobilephones 4,6,8, via the wireless communication means. The projectiondevices 104,106, 108 in each of the other mobile phones 4,6,8, comprisea receiver 40,60,80 which receives adjustment commands sent by thecontroller 24. It is also possible for projection device 102,104,106,108of each of the mobile phones 2,4,6,8 to comprise its own detector 22 anda controller 24. The detector 22 and controller 24 of each mobile phonecan co-operate with the detectors 22 and controllers 24 of the othermobile phones to achieve the desired co-operation of the images on thedisplay surface. Alternatively, if each of the projection device102,104,106,108 of each of the mobile phones 2,4,6,8 comprises adetector 22 and controller 24, then the detector 22 and controller 24 ofone of the mobile phones 2,4,6,8 may be designated as the “master” andthe detectors 22 and controllers 24 of the other mobile phone designatedas the “slaves”. The “master” detector 22 and controller 24 may effectadjustment of the projection devices 102, 104, 106, 108 in the othermobile phones 2,4,6,8.

The brightness of each of the images 12,14,16,18 visible on the displaysurface 10 is limited by the maximum brightness of the light which canbe provided by the light source 120 in each projection device102,104,106,108. Overlapping the images 12,14,16,18 projected by eachprojection device 102,104,106,108 on the display surface 10 will displaya single, brighter image, on the display surface 10.

To achieve overlapping of the images 12,14,16,18 on the display surface10 a user may simply orientate the mobile phones 2,4,6,8 so that theirrespective projection devices 102,104,106,108 each project to the sameposition on the display surface 10. Accordingly, if the projectiondevice 102,104,106,108 of each mobile phone 2,4,6,8 projects the sameimage 12,14,16,18 the images will overlap so that a single image isvisible on the screen. As the single image is formed by the lightprojected by all four of the projection devices 102,104,106,108 thedisplayed single image will appear brighter on the display surface 10.

Alternatively, to achieve overlapping of the images 12,14,16,18, thedetector 22 in projection device 102 detects the position of each of theimages 12,14,16,18 on the display surface 10. The detector 22 alsodetects the brightness of each image, the shape of each image and thedimensions of each image 12,14,16,18. The detector 22 passes imageposition information, image size information, image shape informationand image brightness information, for each of the images 12,14,16,18, tothe controller 24.

Based on the image position information provided by the detector 22, thecontroller 24 calculates an optimum position on the display surface 10at which the images 12,14,16,18, should be overlapped. The optimumposition is the position on the display surface 10 which is closest toeach of the projected images (i.e., the average position); therefore,overlapping the images 12,14,16,18 at the optimum position which willensure minimal overall adjustment of the projection devices102,104,106,108 is required in order to achieve the desired overlappingof images 12,14,16,18 on the display surface 10. In the present examplethe controller 24 has calculated that the optimum position on thedisplay surface 10 for overlapping of images 12,14,16,18 is position 30.Accordingly, the controller 24 will adjust each of the projectiondevices 102,104,106,108 such that they each project their respectiveimages 12,14,16,18 to position 30 on the display surface 10.

To adjust the projection device 102 such that it projects its image 12to position 30 on the display surface, the controller 24 adjusts the ACactuation signal, which is applied to piezoelectric actuators (notshown) (it will be understood that other types of actuators could alsobe used) that oscillate the MEMS micro-mirror 132 within the projectiondevice 102 about the two oscillation axes 134,136, to include a DCoff-set. It will be understood that the actuators may take any suitableform and are not limited to piezoelectric actuators; for example theactuators may be magnetic, electrostatic, thermal, or electro-magnetic.The application of a DC off-set to the AC actuation signal causesoff-setting of the position of the MEMS micro mirror 132 so that theimage 12 is projected to position 30 on the display surface 10.Comparing the current position of the image 12 with the optimum position30, the controller 24 calculates the amplitude of DC off-set to beapplied to the AC actuation signal.

To adjust the other projection devices 104,106,108 such that they eachproject their respective images 14,16,18 to position 30 on the displaysurface 10, the controller 24 sends an adjustment command, via thewireless communication means, to each of the other projection devices104,106,108. The adjustment commands are received by the receivers 40,60, 80 of each projection device 104,106,108. Each adjustment command,when executed within the projection device 104,106,108, will effectadjustment of the AC actuation signal, which is applied to piezoelectricactuators (not shown) to oscillate the respective MEMS micro-mirrors 132within each projection device 104,106,108 about the two oscillation axes134,136, to include a DC off-set. In each projection device 104,106,108the application of a DC off-set to the AC actuation signal causesoff-setting of the position of the MEMS micro mirror 132 within thatprojection device 104,106,108 so that the projection device 104,106,108projects its image 14,16,18 to position 30 on the display surface 10.For each projection device 104,106,108 the required amplitude of DCoff-set to be applied to the AC actuation signal is calculated by thecontroller 24 by comparing the current position of the image 14,16,18projected by that projection device 104,106,108, with the optimumposition 30. As each mobile phone 2,4,6,8 has a different orientation,the MEMS micro mirror 132 of each projection device 104,106,108 willrequire a different adjustment, consequently the amplitude of DC off-setto be applied to the AC actuation signal in each projection device104,106,108 will be different for each projection device 104,106,108.

Once the required DC off-set has been applied to the AC actuation signalin each projection device 102,104,106,108, the projection device102,104,106,108 of each mobile phone 2,4,6,8 will project theirrespective images 12,14,16,18 to the same position on the displaysurface (i.e., to optimum position 30) so that the images 12,14,16,18overlap at optimum position 30.

To display a single image of increased brightness the overlapping images12,14,16,18 should each be the same size. To adjust the size of theimage 12,14,16,18 projected by a projection device 102,104,106,108, thecontroller 24 adjusts the amplitude of the AC actuation signal which isapplied to piezoelectric actuators to oscillate the MEMS micro-mirrors132 within each projection device 102,104,106,108. Based on the imagesize information provided by the detector 22 the controller 24calculates an optimum image size. The optimum image size will be theaverage size of each of the four projected images 12,14,16,18, thus willbe the image size which can most efficiently be achieved as it willrequired the least overall adjustment of the projection devices102,104,106,108. For each projection device 102,104,106,108, using theimage size information provided by the detector 22, the controller 24determines whether that projection device 102,104,106,108 should beadjusted to increase the size of the image 12,14,16,18, or adjusted todecrease the size of the image 12,14,16,18, to achieve the optimum imagesize.

To increase the size of an image 12,14,16,18 the controller 24 increasesthe amplitude of the AC actuation signal, which is applied topiezoelectric actuators to oscillate the MEMS micro-mirror 132 withinthat projection device 102,104,106, 108. Increasing the amplitude of theactuation signal increases the amplitude of oscillations of the MEMSmicro-mirror 132 about at least one of its oscillation axes 134,136(e.g. the oscillation axis about which the MEMS micro mirror 132oscillates to scan light along the horizontal axis). Increasing theamplitude of the oscillations of the MEMS micro-mirror 132 about atleast one of its oscillation axes 134,136 will ensure light is scannedacross a larger area of the display surface 10, thus the image12,14,16,18 will be projected over a larger area of the display surface10 to provide a larger image. Conversely, to decrease the size of animage 12,14,16,18 the controller 24 decreases the amplitude of the ACactuation signal which is applied to piezoelectric actuators tooscillate the MEMS micro-mirror 132 within that projection device102,104,106, 108. Decreasing the amplitude of the AC actuation signaldecreases the amplitude of oscillation of the MEMS micro-mirror 132about at least one of its oscillation axes 134,136 (e.g., theoscillation axis about which the MEMS micro mirror 132 oscillates toscan light along the horizontal axis). Decreasing the amplitude ofoscillations of the MEMS micro-mirror 132 about at least one of itsoscillation axes 134,136 will ensure light is scanned across a smallerarea of the display surface 10, thus the image 12,14,16,18 will beprojected over a smaller area of the display surface 10 to provide asmaller image.

Based on the size information for the images 12,14,16,18 provided by thedetector 22, the controller 24 calculates the size adjustment requiredfor each image 12,14,16,18 so that each image has a size equal to theoptimum image size. In the present example the optimum image size isillustrated as a dashed line at position 30 of the display surface 10.To achieve the optimum image size the image 12 projected by projectiondevice 102 should be reduced in size and images 14,16, and 18 projectedby projection devices 104,106,108 should each be increased in size.Based on the size information for the images 12,14,16,18 provided by thedetector 22, the controller 24 calculates the reduction in image sizerequired for image 12 and equates this reduction in image size to arequired reduction in amplitude for the AC actuation signal used tooscillate the MEMS micro-mirror 132. The controller 24 subsequentlyreduces the amplitude of the AC actuation signal in projection device102 accordingly. Based on the size information provided by the detector22, the controller 24 also calculates the increase in image sizerequired for each of images 14,16,18 and equates each increase in imagesize to a required increase in amplitude for the AC actuation signalsused in each projection device 104,106,108 to oscillate the MEMSmicro-mirror 132. The controller 24 subsequently sends adjustmentcommands to each of projection devices 104,106,108 which affect therequired increase in the amplitudes of the AC actuation signals whenexecuted within the respective projection device 104,106,108. Once theamplitudes of the MEMS mirror actuation signals in each projectiondevice 102,104,106,108 have been adjusted by the controller 24, the samesized image 12,14,16,18 will be projected by each of the projectiondevices 102,104,106,108 at optimum position 30 on the display surface10.

Additionally, or alternatively, the size of the image 12,14,16,18projected by a projection device 102,104,106,108 may be adjusted bychanging the modulation of the light source 120 in the projection device102,104,106,108. The controller 24 may increase the rate at which lightpulses are generated by the light source 120 within a projection device102,104,106,108 to decrease the size of the image 12,14,16,18 projectedby that projection device 102,104,106,108. An increase in the rate atwhich light pulses 4 are generated causes successive light pulses 4 toreach the MEMS micro mirror 132 of a projection device 102,104,106,108at a faster rate which in turn means that successive light pulses 4 areprojected to the display surface 10 at a faster rate. Since each lightpulse 4 corresponds to a pixel of the projected image 12,14,16,18, thepixels will be closer together on the display surface 10 as the timebetween consecutive light pulses 4 is less and the speed of oscillationof the MEMS micro mirror has remained unchanged. Accordingly, a smallerimage 12,14,16,18 will be visible on the display surface 10.Furthermore, given that the light pulses 4 are generated at a higherrate the light pulses 4 corresponding to each a row of pixels areprojected onto the display surface 10 before the MEMS micro mirror 132has completed an oscillation. Accordingly, the row of pixels will bedisplayed over a smaller span of the display surface 10. The same willbe true for each row of pixels. Accordingly, the image 12,14,16,18 willbe displayed over a smaller area of the display surface 10.

Optionally, the speed of oscillation of the MEMS micro mirror 132 withineach projection device 102,104,106,108 may also be adjusted tocompensate for the effects of laser modulation. For example, the speedof oscillation of the MEMS micro mirror 132 may be increased to ensurethat the distance between successive pixels is not reduced by anincrease in the rate at which the light source 120 generates lightpulses 4.

It will be understood that each projection device 102,104,106,108 couldbe simultaneously adjusted by the controller 24 for image size and imageposition.

FIG. 4 provides a perspective view of the mobile phones after eachprojection device 102, 104,106,108 of each mobile phone 2,4,6,8 has beenadjusted to project an image of the same size (optimum size) to theoptimum position 30. Each of the projection devices 102, 104, 106, 108projects the same image onto the display surface 10. Accordingly, asshown in FIG. 4, the image projected by each projection device overlapson the display surface to display a single image 31 at position 30. Thesingle image 31 has an overall brightness which is greater than thebrightness of an image which could be projected by any of the projectiondevices 102, 104,106,108 alone. The overlapping of the images on thedisplay surface 10 allows the light projected by each projection device102, 104, 106, 108 to be combined on the display surface 10, to form abrighter image 31.

Instead of adjusting each projection device 102, 104,106,108 so that theprojected images overlap on the display surface 10, the controller 24may alternatively adjust each projection devices 102, 104,106,108 sothat the projected images are in alignment on the display surface 10. Asillustrated in FIG. 5, the images 12,14,16,18 projected by eachprojection device 102, 104,106,108 align on the display surface 10 toform a single, larger complete image 41. The images 12,14,16,18projected by each projection device 102, 104,106,108 each form adifferent part of the complete image 41; image 12 projected byprojection device 102 forms the bottom left quarter of the completeimage 41, image 14 projected by projection device 104 forms the top leftquarter of the complete image 41, image 16 projected by projectiondevice 106 forms the bottom right quarter of the complete image 41,image 18 projected by projection device 108 forms the top right quarterof the complete image 41. The images 12,14,16,18 combine, similar topieces of a jig-saw, to display a single complete image 41 on thedisplay surface 10. The resulting image displayed on the display surface10 is larger than an image (of the same brightness) which could beprojected by any of the projection devices 102, 104,106,108 alone.

The controller 24 adjusts each projection device 102, 104,106,108 sothat the images 12,14,16,18 projected by each projection device 102,104,106,108 precisely align on the display surface 10. Precise alignmentof the projected images 12,14,16,18 ensures that the complete image 41,is without gaps, spaces or borders (For example, there exists no gapbetween image 12 and any of the other images 14,16,18). Using theposition information provided by the detector 22, the controller 24adjusts each projection device 102,104,106,108 so that each projectiondevice 102,104,106,108 projects an image to a desired position on thedisplay surface 10. The controller 24 adjusts each projection device102,104, 106, 108 in a similar manner as previously described (i.e., byadjusting AC actuation signal actuation signals used to oscillate theMEMS micro-mirror 132, to include a DC off-set), to achieve alignment ofthe projected images 12,14,16,18.

As well as adjustment of the projection devices for image size andposition, the controller 24 may further adjust each projection device102,104,106,108 such that the brightness of each image projected by eachprojection device 102,104,106,108 is the same. This is particularlyuseful when the images projected by each projection device102,104,106,108 are to be aligned rather than overlapped, as it allowsfor the complete image 41 visible on the projection display surface 10to have a uniform brightness.

Based on the brightness of each image 12,14,16,18 detected by thedetector 22, the controller 24 can determine the adjustment required foreach projection device 102,104,106,108 such that each projection device102,104,106,108 projects an image at a predetermined brightness. Thepredetermined brightness may be the average of the brightness of all theprojected images 12,14,16,18 detected by the detector 22. The controller24 adjusts the light source 120 within the projection device 102 toincrease or decrease the brightness of the projected light to thepredetermined brightness. For projection devices 104,106,108 thecontroller 24 sends adjustment commands to each of the projectiondevices 104,106,108 which when executed adjusts the light sources 120within each of the projection devices 104,106,108 to increase ordecrease the brightness of the projected light to the predeterminedbrightness.

Various modifications and variations to the described embodiments of theinvention will be apparent to those skilled in the art without departingfrom the scope of the invention as defined in the appended claims.Although the invention has been described in connection with specificpreferred embodiments, it should be understood that the invention asclaimed should not be unduly limited to such specific embodiment.

1. A projection device, which is configured to project an image which isco-operable with images projected by one or more other projectiondevices, wherein the projection device comprises: a detector operable todetect characteristics of images projected on a display surface by theprojection device and one or more other projection devices, and acontroller operable to adjust the projection device and to adjust one ormore of the other projection devices, based on the characteristics ofthe images detected by the detector, such that the images projected byeach projection device co-operate on the display surface, by overlappingor aligning.
 2. A projection device according to claim 1, wherein, thedetector is configured to detect at least one of the characteristics ofthe images selected from the group comprising; the position of theimages on the display surface; the size of the images on the displaysurface; the shape of the images on the display surface; the brightnessof the images.
 3. A projection device according to claim 1, wherein thecontroller is operable to adjust the projection device and the one ormore other projection devices, based on the characteristics of theimages detected by the detector, to change the size, position, shape,and brightness of the image projected by the projection device.
 4. Aprojection device according to claim 1, wherein the controller isoperable to off-set a reflective surface in the projection device and areflective surface in the one or more other projection devices, tochange the position on the display surface which the projection deviceand one or more other projection devices project their images, such thatthe images projected by each projection device co-operate on the displaysurface.
 5. A projection device according to claim 1, wherein thecontroller is operable to modify the modulation of a light source in theprojection device and the modulation of a light source in the one ormore other projection devices, such that each projection device projectsan image which defines part of a complete image, and wherein the imagesprojected by each projection device can co-operate to define a completeimage on the display surface.
 6. A projection device according to claim1, wherein the controller is operable to adjust the projection devicesuch that a projection device projects one of either an overexposedimage, underexposed image or correctly exposed image, and wherein thecontroller is operable to adjust at least one other projection devicesuch that the at least one other projection device projects one of anoverexposed image, underexposed image or correctly exposed image,wherein the exposure of the image projected by the projection device isdifferent to the exposure of the image projected by the at least oneother projection device, wherein the projected images cooperate on thedisplay surface to define a single image which has improved brightnessand clarity.
 7. A projection device according to claim 1, wherein theprojection device comprises a means for detecting irregularities on adisplay surface, and a means to adjust the projection device and one ormore other projection devices, to compensate for the detectedirregularities of the display surface.
 8. A projection device accordingto claim 7, wherein the means for detecting irregularities on a displaysurface may comprise a means for projecting a test image, a means formeasuring characteristics of the projected test image and comparing themeasured characteristics to a predefined set of ideal characteristics todetermine how the display surface has altered the projected test image,and a means for determining one or more characteristics of a displaysurface on the basis of how the display surface has altered theprojected test image.
 9. The projection device according to claim 1,further comprising a means for detecting an interaction of a user with aprojected image.
 10. A projection device according to claim 1, whereinthe controller is operable to calculate an optimum position on thedisplay surface for projection of the image, wherein the optimumposition is the position on the display surface at which a projectiondevice should project, so that minimum overall adjustment of theprojection device and one or more other projection devices will berequired to achieve co-operation of the images on the display surface.11. A projection device according to claim 1, wherein the projectiondevice is configured to enable a user to select a position on thedisplay surface at which the images projected by the projection deviceand one or more projections devices will co-operate, wherein theprojection device is operable to project to a plurality of positions ona display surface where co-operation of the images can take place, andwherein the projection device is further configured to enable a user toselect one of the plurality of positions.
 12. A projection deviceaccording to claim 1, comprising a first mirror which is configured suchthat it can oscillate along an oscillation axis to scan light on thedisplay surface; and a second mirror which is configured such that itcan oscillate along an oscillation axis to scan light on the displaysurface, wherein the first and second mirrors are in opticalcommunication; wherein the first mirror is configured to oscillatefaster than the second mirror; and wherein the projection device furthercomprises a means to adjust the projection device such that the secondmirror can scan light in the horizontal direction and the first mirrorcan scan light in the vertical direction.
 13. A projection device, whichis configured to project an image which is co-operable with imagesprojected by one or more other projection devices, wherein theprojection device comprises: a receiver, configured to receive commandsfrom a projection device according to claim
 1. 14. A mobile devicecomprising a projection device according to claim 1.